U.S. patent application number 16/879102 was filed with the patent office on 2020-09-03 for soil and dirt repellent powder coatings.
The applicant listed for this patent is ARMSTRONG WORLD INDUSTRIES, INC.. Invention is credited to Kenneth G. CALDWELL, Steven L. MASIA, Michelle X. WANG.
Application Number | 20200277511 16/879102 |
Document ID | / |
Family ID | 1000004843246 |
Filed Date | 2020-09-03 |
United States Patent
Application |
20200277511 |
Kind Code |
A1 |
MASIA; Steven L. ; et
al. |
September 3, 2020 |
SOIL AND DIRT REPELLENT POWDER COATINGS
Abstract
A dirt repellant panel coated with a powder coating composition
that includes a polymeric binder and an anionic fluorosurfactant
present in an amount ranging from about 0.1 wt. % to about 4 wt.
%.
Inventors: |
MASIA; Steven L.;
(Lancaster, PA) ; WANG; Michelle X.; (Lititz,
PA) ; CALDWELL; Kenneth G.; (Mountville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARMSTRONG WORLD INDUSTRIES, INC. |
Lancaster |
PA |
US |
|
|
Family ID: |
1000004843246 |
Appl. No.: |
16/879102 |
Filed: |
May 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15924848 |
Mar 19, 2018 |
10696864 |
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16879102 |
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14746313 |
Jun 22, 2015 |
9920219 |
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15924848 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 5/02 20130101; C09D
133/064 20130101; C08K 9/04 20130101; C09D 5/033 20130101; C08K
5/0041 20130101; C08G 2150/20 20130101; C08K 5/521 20130101; C08K
5/49 20130101; C08G 18/80 20130101; C09D 133/14 20130101; C09D
167/00 20130101; C08G 18/42 20130101; C09D 133/068 20130101; C09D
5/1681 20130101; C09D 175/04 20130101; C09D 175/06 20130101 |
International
Class: |
C09D 175/06 20060101
C09D175/06; C09D 175/04 20060101 C09D175/04; C09D 5/03 20060101
C09D005/03; C09D 5/16 20060101 C09D005/16; C08G 18/80 20060101
C08G018/80; C08K 5/521 20060101 C08K005/521; C09D 167/00 20060101
C09D167/00 |
Claims
1. A method of forming a dirt repellant panel comprising: a)
applying a powder coating precursor to a substrate, the powder
coating precursor comprising a mixture of polymeric resin,
cross-linker, and anionic fluorosurfactant; b) heating the powder
coating precursor to a curing temperature such that the polymeric
resin and cross-linker chemically react to form a cured powder
coating atop the substrate; and wherein the polymer resin is
substantially free of fluoro-carbon groups.
2. The method according to claim 1, wherein the curing temperature
of step b) ranges from about 190.degree. C. to about 210.degree.
C.
3. The method according to claim 1, wherein the powder coating
precursor has a solids content of 100%.
4. The method according to claim 1, wherein the anionic
fluorosurfactant is present in an amount ranging from 0.05 wt. % to
4 wt. % based on the total weight of the powder coating.
5. The method according to claim 1, wherein the cured powder
coating is substantially free of fluoropolymer.
6. The method according to claim 1 wherein the anionic
fluorosurfactant comprises a phosphate group substituent.
7. The method according to claim 1 wherein the anionic
fluorosurfactant has a melting point ranging from 50.degree. C. to
70.degree. C.
8. The method according to claim 1 wherein the polymer resin has a
glass transition temperature ranging from 45.degree. C. to
90.degree. C.
9. The method according to claim 1, wherein the powder coating
precursor further comprises a pigment in an amount ranging from 10
wt. % to 30 wt. % based on the total weight of the powder coating
precursor.
10. A method of forming a dirt repellant panel comprising: a)
melt-mixing a blend of polymeric resin, cross-linker, anionic
fluorosurfactant, and pigment; b) pelletizing the blend of step a)
into a powder coating precursor; c) applying the powder coating
precursor of step b) to a substrate; and d) heating the powder
coating precursor mixture to a curing temperature such that the
polymeric resin and cross-linker chemically react to form a cured
powder coating atop the substrate; wherein the polymeric resin is
substantially free of fluoro-carbon groups.
11. The method according to claim 10, wherein the blend of step a)
has a solids content of 100%.
12. The method according to claim 10, wherein the cured powder
coating is substantially free of fluoropolymer.
13. The method according to claim 10, wherein the anionic
fluorosurfactant is present in an amount ranging from about 0.05
wt. % to about 4 wt. % based on the total weight of the powder
coating precursor.
14. The method according to claim 10, wherein the melt-mixing of
step a) is performed at a temperature ranging from about 90.degree.
C. to about 150.degree. C.
15. The method according to claim 10, wherein step a) is performed
in an extruder.
16. The method according to claim 10, wherein the curing
temperature of step b) ranges from about 190.degree. C. to about
210.degree. C.
17. A method of forming a dirt repellant panel comprising: a)
pretreated pigment with an anionic fluorosurfactant to form a
pretreated pigment b) mixing the pretreated pigment with a polymer
binder to form a powder coating precursor mixture that is
substantially free of solvent; c) applying the powder coating
precursor mixture to a substrate; and d) curing the powder coating
precursor mixture to form the dirt repellant panel; wherein the
polymer binder is substantially free of fluoro-carbon groups and
the anionic fluorosurfactant is present in an amount ranging from
10 wt. % to 25 wt. % based on the total weight of the pigment.
18. The method of forming the dirt repellant panel of claim 17,
wherein during step b), the polymer binder and the pretreated
pigment are mixed in an extruder at a temperature ranging from
90.degree. C. to 110.degree. C.
19. The method of forming the dirt repellant panel of claim 18,
wherein subsequent to step b) and prior to step c), the powder
coating mixture is pelletized.
20. The method of forming the dirt repellant panel of claim 19,
wherein the anionic fluorosurfactant is present in an amount
ranging from about 0.05 wt. % to about 4.0 wt. % based on the total
weight of the powder coating precursor mixture.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 15/924,848 filed on Mar. 19, 2018, which is a divisional
of U.S. patent application Ser. No. 14/746,313 filed on Jun. 22,
2015. The disclosure of the above application is incorporated
herein by reference.
FIELD OF INVENTION
[0002] The present invention is directed to soil and dirt repellent
powder coatings comprising anionic fluorosurfactants
BACKGROUND
[0003] It is known that certain fluoro-carbon containing polymers
and siloxane containing polymers may be able to add dirt-resistant
properties to paints and other solvent-based coatings. However,
previously, large quantities of such fluoro-carbon and siloxane
containing polymers were required by the overall formulation--in
order to obtain the desired dirt-resistant properties in the
resulting coating. As such, the resulting balance between the
dirt-resistant properties of the exposed surface of the coating and
the coatings ability to adhere to the underlying substrate was
undermined. Thus there exists a need to provide dirt-resistant
coatings--specifically soil and dirt repellant coatings--that
achieve the desired exposed surface repellency, while not
undermining the bond strength to the underlying substrate. A powder
coating system can benefit from such dirt-resistant properties, but
unlike typical paints and coatings, it has additional constraints
that it is desirable to be a solvent free system.
SUMMARY
[0004] Some embodiments of the present invention include a dirt
repellant panel comprising a substrate and a powder coating applied
to the substrate. In some embodiments, the powder coating is formed
from a mixture comprising a blend of polymer resin, cross-linker,
and a surfactant composition. In some embodiment, the polymer resin
is substantially free of fluoro-carbon groups. The surfactant
composition may be solvent-free and comprise an anionic
fluorosurfactant. According to some embodiments, the anionic
fluorosurfactant may be present in an amount ranging from 0.05 wt.
% to 4 wt. % based on the total weight of the powder coating
composition.
[0005] Some embodiments of the present invention include a powder
coating composition comprising a blend of a binder comprising a
polymer resin that is substantially free of fluoro-carbon groups;
and a pigment that is pre-treated with an anionic fluorosurfactant;
wherein the blend is substantially free of solvent.
[0006] According to some embodiments, the present invention is
directed to a dirt repellant panel comprising a substrate and a
powder coating applied to the substrate. The powder coating may be
formed from a mixture that is substantially free of solvent. In
some embodiments, the mixture comprises a binder and a pigment. In
some embodiments, the mixture comprises a polymer resin that is
substantially free of fluoro-carbon groups. In some embodiments,
the pigment is pre-treated with an anionic fluorosurfactant.
[0007] In some embodiments, the present invention is directed to a
method of forming a dirt repellant panel. The method may include a
first step of preparing a powder coating comprising a polymer
binder, a pigment, and an anionic fluorosurfactant. The method may
further include a second step of applying the powder coating to a
substrate. The method may further include a third step of curing
the powder coating to form the dirt repellant panel. In some
embodiments, the dirt repellant coated substrate is a ceiling tile
or panel. According to some embodiments of the present invention,
the polymer binder is substantially free of fluoro-carbon groups
and the anionic fluorosurfactant is present in an amount ranging
from 10 wt. % to 25 wt. % based on the total weight of a single
pigment.
DETAILED DESCRIPTION
[0008] The present invention is directed to soil and dirt repellant
panels comprising a substrate and a powder coating layer that is
applied to the substrate. The powder coating exhibits soil and dirt
repellant characteristic based on the inclusion of anionic
fluoro-compounds. The powder coating is formed from a high-solids
precursor mixture of a binder composition and cross-linker. The
precursor mixture may be reacted at an elevated temperature to form
the fully cured powder coating composition, as discussed herein. In
some embodiments, the precursor mixture has a solids content of
100% and is substantially free of solvent.
[0009] The binder composition may include a polymeric resin that
can react with the cross-linker during curing, as discussed herein,
thereby forming the fully cured matrix composition. According to
some embodiments, the polymeric resin of the present invention to
have specific material properties, including glass transition
temperature, molecular weight, functionality, melt viscosity, and
film formation and leveling properties. Without proper
consideration to the above references material properties,
selecting the undesirable polymeric resin may result in a
composition that is unsuitable for powder coatings as the resulting
precursor mixture may exhibit poor shelf-life and inadequate flow
properties during processing, and the resulting powder coating may
exhibit inadequate film formation characteristics rendering the
coating inoperable.
[0010] According to the present invention, the polymeric resin
should comprise at least one polymeric composition having a glass
transition temperature (Tg) that is greater than room temperature,
preferably at least about 50.degree. C. According to some
embodiments of the present invention, the polymeric resin may have
a Tg that is about 50.degree. C. According to some embodiments of
the present invention, the polymeric resin may have a Tg that is
about 60.degree. C. According to some embodiments of the present
invention, the polymeric resin may have a Tg that is about
70.degree. C. For the purposes of the present invention, the term
"about" means+/-5%.
[0011] Selecting the correct glass transition temperature of the
polymeric resin is an important consideration for powder coating
applications as a Tg that is too low may result in a precursor
mixture that cannot resist sintering and agglomeration during
storage and/or shipping of the mixture, thereby degrading the
shelf-life of the precursor mixture. Conversely, since powder
coatings have high solids contents, selecting a polymeric resin
that has a Tg that is too high may result in a precursor mixture
that does not exhibit adequate flow during processing or leveling
properties after application, thereby resulting in an un-evenly
applied powder coating composition. The Tg of a polymeric resin can
be controlled through the selection of a number of parameters
including, but not limited to, molecular weight, type of polymeric
backbone, and the degree of crystallinity, as discussed herein.
[0012] The flow properties of the polymeric resin are measured by a
melt viscosity. At high solids content (preferably 100% solids,
free of solvent), the obtaining a low melt viscosity is a
consideration to ensure maximum flow of the polymeric resin during
processing. As a polymeric resin is processed during mixing and
curing (as discussed herein), the polymeric resin begins to react
with a curing agent, also referred to as a cross-linker, that is
present in the precursor mixture thereby creating a significant
increase in viscosity of the precursor mixture as it becomes the
fully cured powder coating. Therefore, using a polymeric resin that
exhibits a low melt viscosity is a criteria to ensure that there is
ample time for the precursor mixture to mix and flow through the
processing unit (as discussed herein) before the precursor mixture
has reacted a degree of cross-linking that approaches the fully
cured powder coating. The melt viscosity of a polymeric resin is
the result of a number of factors that include: molecular weight,
functionality, and type of polymeric backbone, as discussed herein.
The specific melt viscosities of the polymeric resin and overall
precursor mixture will be discussed herein.
[0013] According to the present invention, the polymeric resin
should comprise at least one polymeric composition having a weight
average (Mw) molecular weight that ranges from about 1,500 to
15,000. In some embodiments of the present invention, the polymeric
resin may have a weight average (Mw) that ranges from about 15,000
to 30,000. The molecular weight of the polymeric resin impacts the
flexibility, impact strength, and processesability of the powder
coating (i.e. melt viscosity). Polymeric resins having a greater
molecular weight (Mw) exhibit greater melt viscosities as compared
to lower weight (Mw) polymeric resins
[0014] In a preferred embodiment, the polymeric resin having a
molecular weight (Mw) ranging from about 1,500 to about 15,000 has
a polydispersity of about 1. Polydispersity is a ratio of weight
average (Mw) molecular weight to number average (Mn) molecular
weight of a polymeric composition. Having a polydispersity of about
1 ensures that the physical properties of the resulting powder
coating (i.e., flexibility, impact strength) are maximized without
sacrificing a desired low melt viscosity of the precursor mixture
during processing. The low melt viscosity being suitable when
processing at a high solids content (preferably solve-free)
precursor mixture, as may be required for the powder coating
according to some embodiments of the present invention.
[0015] According to some embodiments, forming a three-dimensional,
cross-linked polymeric network that forms the powder coating of the
present invention requires that the polymeric resin comprises a
polymer having an average of at least two functional groups that
are available to react with functional groups present on the
cross-linker. In some embodiments, the polymeric resin may have an
average number of functional groups, the average ranging from 2 to
10 functional groups. In some embodiments, the polymeric resin may
have a backbone that is linear or branched and the placement of the
functional groups will depend on the type of backbone of the
polymeric resins. In some embodiments, the polymeric resin is a
linear polymer having two to four functional groups positioned at
the terminal ends of the polymer. The functional groups of the
polymeric resin may be selected from hydroxyl groups, carboxylic
acid groups, isocyanate groups, epoxy groups, acrylic groups and a
combination thereof. In some embodiments, the functional groups of
the polymeric binder may be temporarily blocked as discussed
herein.
[0016] According to some embodiments of the present invention, the
polymeric resin may comprise polymer having a backbone with
moieties selected from ester groups, urethane groups, carbonate
groups, epoxy groups and a combination thereof.
[0017] In some embodiments, the binder composition includes a
polymeric resin selected from polyester resin, polyurethane resin,
epoxy resin, and polyester-urethane acrylate resin. Suitable
polyester resins may be hydroxyl-functional (OH) or
carboxyl-functional (COOH). The polyester resin may be the reaction
product of a polycarboxylic acid and a polyol. For the purposes of
this invention, the term polycarboxylic acid includes compounds
having at least two carboxylic acid groups. For the purposes of
this invention, the term polyol includes compounds having at least
two hydroxyl groups. For hydroxyl-functional polyester, the polyol
is present relative to the polycarboxylic acid in an OH:COOH
stoichiometric excess that ranges from 2:1 to 6:1. Excess polyol
ensures that all free carboxylic acid groups are consumed while
allowing excess hydroxyl groups to remain unconsumed during the
esterification reaction. The hydroxyl groups may be present at the
terminal ends of the polyester. For carboxyl-functional polyester,
the polycarboxylic acid is present relative to the polyol in a
COOH:OH stoichiometric excess that ranges from 2:1 to 6:1. Excess
polycarboxylic acid ensures that all free hydroxyl groups are
consumed while allowing excess carboxylic acid groups to remain
unconsumed during the esterification reaction. The carboxylic acid
groups may be present at the terminal ends of the polyester.
[0018] The condensation reaction of hydroxyl-functional and
carboxyl-functional compounds to form the polyester resin may be
aided by a catalyst. In some non-limiting embodiments, the catalyst
may be selected from N-methylimidazole, diazabicyclo[2,2,2]octane,
diazabicyclo[5,4,0]undec-7-ene and pentamethyldiethylenetriamine
and mixtures thereof. Other examples of suitable esterification
catalyst include tetrabutyl-o-titanate, stannous octoate, p-toluene
sulphonic acid, and combinations thereof.
[0019] In non-limiting embodiments, the polyol may be a diol, a
triol, or a higher-functional polyol having 4-8 hydroxyl groups
(e.g. tetrol). In some embodiments the polyol may be aromatic,
cycloaliphatic, aliphatic, or a combination thereof. In some
embodiments the carboxyl-functional compound is dicarboxylic acid,
a tricarboxylic acid, a higher functional polycarboxylic acid
having 4-8 carboxylic acid groups, or a combination thereof. In
some embodiments, the polycarboxylic acid may be aliphatic,
cycloaliphatic, aromatic, or a combination thereof.
[0020] In some embodiments the polyol may include a diol that is
selected from alkylene glycols, such as ethylene glycol, propylene
glycol, diethylene glycol, dipropylene glycol, triethylene glycol,
tripropylene glycol, hexylene glycol, polyethylene glycol,
polypropylene glycol and neopentyl glycol; hydrogenated bisphenol
A; cyclohexanediol; propanediols including 1,2-propanediol,
1,3-propanediol, butyl ethyl propanediol, 2-methyl-1,3-propanediol,
and 2-ethyl-2-butyl-1,3-propanediol; butanediols including
1,4-butanediol, 1,3-butanediol, and 2-ethyl-1,4-butanediol;
pentanediols including trimethyl pentanediol and
2-methylpentanediol; cyclohexanedimethanol; hexanediols including
1,6-hexanediol; hydroxy-alkylated bisphenols; polyether glycols,
for example, poly(oxytetramethylene) glycol. In some embodiments,
the polyol may be a triol or higher polyol that is selected from
trimethylol propane, pentaerythritol, di-pentaerythritol,
trimethylol ethane, trimethylol butane, dimethylol cyclohexane,
glycerol and the like.
[0021] In some embodiments the polycarboxylic acid may include a
dicarboxylic acid that is selected from adipic acid, azelaic acid,
sebacic acid, succinic acid, glutaric acid, decanoic diacid,
dodecanoic diacid, phthalic acid, isophthalic acid,
5-tert-butylisophthalic acid, tetrahydrophthalic acid, terephthalic
acid, hexahydrophthalic acid, methylhexahydrophthalic acid,
dimethyl terephthalate, 2,5-furandicarboxylic acid,
2,3-furandicarboxylic acid, 2,4-furandicarboxylic acid,
3,4-furandicarboxylic acid, 2,3,5-furantricarboxylic acid,
2,3,4,5-furantetracarboxylic acid, cyclohexane dicarboxylic acid,
1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic
acid, and anhydrides thereof, as well as mixtures thereof. In some
embodiments the polycarboxylic acid may be selected from
tricarboxylic acids such as trimellitic acid and anhydrides
thereof.
[0022] In some embodiments, suitable polyurethane resins for the
powder coating composition are disclosed, for example, in U.S. Pat.
Nos. 4,404,320, and 4,246,380. Suitable polyester-urethane
acrylates are disclosed, for example, in U.S. Pat. No. 6,284,321.
Suitable epoxy compounds for the powder coating composition are
disclosed, for example, in U.S. Pat. No. 5,732,052.
[0023] The specific type and amount of reactant used to create the
polyester resin has a significant effect on the melt viscosity,
crystallinity, and Tg of the polymeric resin. Specifically,
aromatic and/or cycloaliphatic monomers lead to high Tg polymers,
and longer-chain aliphatic monomers lead to lower Tg polymers. For
example, a polyester resin having a significant level of ester
groups in the backbone that are derived from terephthalic
acid/isophthalic acid can have its Tg lowered by replacing certain
amounts of the terephthalic acid/isophthalic acid with adipic acid,
thereby making the polyester resins more flexible and more likely
to flow at a lower temperature. However, substituting too much
adipic acid will result in the polyester having a Tg that is too
low to be used in powder coating formulations.
[0024] In a non-limiting embodiment, the polymeric resin has a 100%
solids content (i.e. is free of solvent) and has a melt viscosity
ranging from 2,000 mPa/s to 5,000 mPa/s at 200.degree.
C.--including all sub-ranges and integers there between. In the
non-limiting embodiment, the polymeric resin may have a Tg ranging
from about 50.degree. C. to about 70.degree. C. In some
embodiments, the polymeric resin may be hydroxyl-functional and
have a hydroxyl value ranging from about 40 to about 300.
Non-limiting examples of suitable hydroxyl-functional polymeric
resin include hydroxyl-functional polyester resin, such as
commercially available Polymac 3110 and/or Rucote 102. In some
embodiments, the polymeric resin may be carboxyl-functional and
have an acid number ranging from 30 to 50.
[0025] According to some embodiments of the present invention, the
cross-linker comprises at least one low molecular weight compound
having at least two functional groups. The cross-linker may
comprise between 2 and 6 functional groups. In an alternative
embodiment, the cross-linker may comprise between 2 and 4
functional groups. The functional groups of the cross-linker may be
selected from hydroxyl groups, carboxylic acid groups, isocyanate
groups, epoxy groups, and a combination thereof.
[0026] In some non-limiting embodiments, suitable cross-linkers may
include the aforementioned polyol compounds, polycarboxylic acid
compounds, as well as polyisocyanate compounds and epoxy-functional
compounds, such as glycidyl-functional acrylic copolymers. In some
embodiments, the functional groups of the cross-linker may be
temporarily blocked, as discussed herein, thereby enhancing the
shelf-life of the precursor mixture during storage and shipment.
The specific functional group will depend on the desired
composition of the resulting powder coating.
[0027] The specific selection of cross-linker will depend on the
type of polymeric resin and the desired final matrix composition.
For example, hydroxyl functional polyester may be cured with
polycarboxylic acid cross-linker, thereby resulting in a
three-dimensional polyester matrix--with the OH:COOH stoichiometric
ratio of polyester resin to cross-linker being about 1:1 to ensure
all functional groups on both the polymeric resin and cross-linker
are consumed during the esterification cross-linking reaction.
[0028] The hydroxyl functional polyester may alternatively be cured
with polyisocyanate cross-linker, thereby resulting in a
polyester-polyurethane matrix. The OH:NCO ratio of polyester resin
to polyisocyanate cross-linker being essentially 1:1 to ensure that
all functional groups on both the polymeric resin and cross-linker
are consumed during the urethane forming cross-linking reaction.
For the purposes of this invention, the term polyisocyanate refers
to isocyanate-functional compounds having at least two isocyanate
functional groups, such as diisocyanate, isocyanurate, biuret,
isocyanurate allophanates. In a preferred embodiment, the polymeric
resin is the polyester-polyurethane resin.
[0029] The polyisocyanate of the present invention may be selected
from compounds such as isophorone diisocyanate (IPDI),
4,4'-dicyclohexylmethane-diisocyanate, and
trimethyl-hexamethylene-diisocyanate, 1,6-hexamethylene
diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate,
octadecylene diisocyanate and 1,4 cyclohexylene diisocyanate.
toluene diisocyanate; methylenediphenyl diisocyanate; tetra
methylxylene diisocyanate, and isocyanurates, biurets, allophanates
thereof, as well as mixtures thereof, as well as adducts,
isocyanurates, biurets, and allophanates thereof. In one
embodiment, the polyisocyanate comprises IPDI.
[0030] According to some embodiments of the present invention, each
of the free isocyanate groups present on the cross-linker may be
temporarily blocked with a blocking agent to ensure no premature
reacting of the hydroxyl-groups and isocyanate groups occur before
final curing--thereby extending the shelf-life of the precursor
mixture during storage and shipment. Suitable blocking agents may
include, for example, secondary or tertiary alcohols such as
isopropanol or tert-butanol; C--H acidic compounds such as malonic
dialkyl ester, acetylacetone, and acetoacetic alkyl ester, oximes
such as formaldoxime, acetaldoxime, methyl ethyl ketone oxime,
cyclohexanone oxime, acetophenone oxime, benzophenone oxime or
diethylglyoxime, lactams such as .epsilon.-caprolactam,
.delta.-valerolactam, .gamma.-butyrolactam, phenols such as phenol,
o-methylphenol; N-alkylamides such as N-methylacetamide, imides
such as phthalimide, secondary amines such as diisopropylamine,
imidazole, pyrazole, and 1,2,4-triazole. In a preferred embodiment,
the cross-linker is .epsilon.-caprolactam blocked IPDI.
[0031] The blocking agent may be employed relative to the free
isocyanate groups in a stoichiometric ratio of about 1:1 to ensure
that all free isocyanate groups present on the cross-linker are
temporarily blocked. The blocking agent prevents the isocyanate
groups from prematurely reacting with moisture or cross-linker at
room temperature, but will deblock from the isocyanate group at an
elevated temperature of at no more than 170.degree. C., thereby
allowing the free isocyanate groups to react with the cross-linker
and form a fully cured matrix.
[0032] In other embodiments, the blocked polyisocyanate may be in
the form of a uretdione modified polyisocyanate. Uretdione modified
polyisocyanates contain two free isocyanate groups as well as two
internally blocked isocyanate groups. The internal blocking of the
isocyanate groups occurs without the need of an external blocking
agent, such as .epsilon.-caprolactam. At elevated temperatures, the
uretdione ring is broken and the two internally blocked isocyanate
groups are made available to react with isocyanate-reactive groups,
such as hydroxyl groups, in a urethane forming reaction. According
to the present invention, the uretdione blocked polyisocyanate may
be formed from the above mentioned polyisocyanate compounds--such
as IPDI. After deblocking, uretdione based on diisocyanates will
contain an equivalent of four isocyanate groups.
[0033] In some embodiments, a catalyst may be added to aid the
urethane-forming reaction between the hydroxyl groups and the
isocyanate groups. The catalyst may be selected from organometallic
catalysts, such as dibutyltin dilaurate or tin octoate, or tertiary
amines, such as triethylamine, pyridine,
N,N-dimethylaminocyclohexane, or 1,4-diazabicyclo[2.2.2]octane.
Other catalysts may be selected from metal ion diacryliodium salts.
The catalyst may be present in an amount ranging from about 0.001
wt. % to about 1 wt. % based on the total weight of the precursor
mixture. This range includes all specific values and subranges
there between, such as 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2,
0.5, and 0.8 wt. % based on the total weight of the precursor
mixture.
[0034] In some embodiments, the polymeric resin may be an
isocyanate terminated urethane-polyester prepolymer. The prepolymer
may be the reaction product of stoichiometric excess of
polyisocyanate relative to hydroxyl-terminated polyester resin, the
NCO:OH ratio ranging from 2:1 to 6:1. Excess isocyanate ensures
that all free hydroxyl groups are consumed during the formation of
the polyurethane prepolymer while ensuring that free isocyanate
groups remain on the prepolymer. Any excess polyisocyanate
remaining after the formation of the prepolymer may be stripped by
low pressure vacuum. The free isocyanate groups present on the
prepolymer may be blocked with previously discussed isocyanate
blocking agents in a stoichiometric ratio of blocking agent to the
free isocyanate of about 1:1 to ensure all free isocyanate groups
present on the prepolymer are temporarily blocked. The blocked
isocyanate-terminated polyester prepolymer may then be mixed with
polyol cross-linker to form a storage stable precursor mixture. The
polyol cross-linker comprises the same low molecular weight polyol
compounds listed with respect to the formation of the polyester
resin.
[0035] In some embodiments, carboxyl functional polyester resin may
be cured with polyol cross-linker, thereby resulting in a polyester
matrix. The free carboxyl groups present on the carboxyl-functional
polyester resin may be present relative to the hydroxyl groups
present on the cross-linker in a COOH:OH stoichiometric ratio of
about 1:1, thereby ensuring that all functional groups present on
both the polyester resin and the cross-linker are consumed during
the esterification cross-linking reaction. The polyol cross-linker
comprises the same low molecular weight polyol compounds listed
with respect to the formation of the polyester resin.
[0036] The carboxyl functional polyester resin may also be cured
with epoxy functional compounds. In some non-limiting embodiments,
the epoxy functional compounds may include epoxy resin that may be
saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or
heterocyclic.
[0037] Examples of epoxy resins suitable for use in the invention
include polyglycidyl ethers of polyhydric compounds, brominated
epoxies, epoxy novolacs or similar polyhydroxyphenol resins,
polyglycidyl ethers of glycols or polyglycols, and polyglycidyl
esters of polycarboxylic acids. Preferably the epoxy resin is a
polyglycidyl ether of a polyhydric phenol. Polyglycidyl ethers of
polyhydric phenols can be produced, for example, by reacting an
epihalohydrin with a polyhydric phenol in the presence of an
alkali. Examples of suitable polyhydric phenols include:
2,2-bis(4-hydroxyphenyl) propane (bisphenol-A;
2,2-bis(4-hydroxy-tert-butylphenyl) propane;
1,1-bis(4-hydroxyphenyl) ethane; 1,1-bis(4-hydroxyphenyl)
isobutane; 2,2-bis(4-hydroxytertiarybutylphenyl) propane;
bis(2-hydroxynapthyl) methane; 1,5-dihydroxynaphthalene;
1,1-bis(4-hydroxy-3-alkylphenyl) ethane and the like.
[0038] According to the present invention, the binder composition
is substantially free of a volatile solvent, excluding moisture
content. For the purposes of this invention, the term
"substantially free" means less than 0.05 wt. % based on the total
weight of the referenced element. In a non-limiting example, a
mixture comprising binder, cross-linker, and filler that is
substantially free of solvent comprises solvent in an amount less
than 0.05 wt. % based on the total weight of the
mixture--preferably less than 0.01 wt. %. According to a preferred
embodiment, the binder composition of the present invention has
100% solids is free of solvent--include volatile organic solvents.
Furthermore, according to additional embodiments of the present
invention, the binder composition is substantially free of polymer
resin comprising fluoro-carbon groups, such as fluoro-modified
polyurethane and fluorpolymer, e.g., PVDF, or PTFE. Stated
otherwise, the polymeric resin, which makes up the binder
composition of the present invention, is substantially free of
fluoro-carbon groups.
[0039] According to some embodiments, the powder coating of the
present invention may further comprise additives, fillers, coating
performance enhancers. Such fillers and additives may include, but
are not limited to, inert fillers, antioxidants, stabilizers,
pigments, reinforcing agents, reinforcing polymer, lubricants,
fungicides, degassers, a surfactant, flow additives, dispersants,
thixotropic agents, adhesion promoters, light stabilizers, flame
retardants, anticorrosion agents, inhibitors, leveling agents,
anti-cratering agents, and mixtures thereof. In some embodiments,
the fungicide may be present in an amount ranging from about 6 wt.
% to about 10 wt. % based on the total weight of the powder coating
composition. In a non-limiting example, the fungicide may comprise
zinc borate, 2-(-4-thiazolyl)benzimidazole.
[0040] In some embodiments, the precursor composition may further
comprise reinforcing polymer, such as acrylic copolymers that
further comprise functional groups capable of reacting with the
functional groups present in the binder. In a non-limiting example,
the reinforcing polymer may comprise glycidyl-functional acrylic
polymer. As previously discussed, glycidyl groups are capable of
reacting with carboxylic acid groups.
[0041] Yet further additives include metals and metal oxides such
as, for instance, chromium oxide, chromium, zinc oxide, copper
oxide, copper, nickel, titanium, stainless steel, aluminum,
titanium dioxide, tin oxide, iron, iron oxide, and the like. Such
metals may serve, for instance, as abrasion-resistant fillers,
compatibilizers, or as pigments. Pigments may further include
compounds such as titanium dioxide, barium sulfate, calcium
carbonate, or a combination thereof. In some embodiments of the
present invention, the pigments may have an average particle size
ranging from 180 nm to 220 nm; in a preferred embodiment, the
pigment has an average particle size of about 200 nm. In some
embodiments, the powder coating according to the present invention
may comprise about 15 wt. % to about 30 wt. % of pigment. According
to some embodiments, the powder coating according to the present
invention may comprise about 20 wt. % of titanium dioxide.
[0042] The surfactant according to the present invention may be
added to the precursor mixture in a surfactant composition prior to
final processing and curing, as discussed herein. The surfactant
composition according to the present invention is substantially
free of solvent--preferably having a solids content of 100% and
substantially free of solvent, including volatile organic solvents.
The surfactant composition according to the present invention is in
powder form at room temperature. The surfactant composition
comprises at least one fluorosurfactant.
[0043] The fluorosurfactant according to the present invention may
have a melting temperature that ranges from about 50.degree. C. to
about 70.degree. C. In some embodiments, the fluorosurfactant of
the present invention has a low pH value--ranging from about 1 to
about 6, including all value and sub-ranges therebetween. In some
embodiments, the fluorosurfactant may be an anionic
fluorosurfactant. The anionic moiety of the fluorosurfactant
according to the present invention is selected from a sulfate,
sulfonate, phosphate, or carboxylate moiety, wherein preferred is a
phosphate moiety. According to some embodiments, the
fluorosurfactant of the present invention may have at least one of
the following formulas:
(R.sub.fAO)P(O)(O.sup.-M.sup.+).sub.2 Formula I
(R.sub.fAO).sub.2P(O)(O.sup.-M.sup.+) Formula II
[0044] wherein R.sub.f is a C.sub.1 to C.sub.16 linear or branched
perfluoroalkyl, which may be optionally interrupted by one, two or
three ether oxygen atoms.
[0045] A is selected from:
(CH.sub.2CF.sub.2).sub.m(CH.sub.2).sub.n;
(CH.sub.2).sub.oSO.sub.2N(CH.sub.3)(CH.sub.2).sub.p;
O(CF.sub.2).sub.q(CH.sub.2).sub.r; or OCHFCF.sub.2OE;
[0046] m is 0 to 4;
[0047] n, o, p, and r, are each independently 2 to 20;
[0048] q is 2;
[0049] E is a C.sub.2 to C.sub.20 linear or branched alkyl group
optionally interrupted by oxygen, sulfur, or nitrogen atoms; a
cyclic alkyl group, or a C.sub.6 to C.sub.10 aryl group;
[0050] M is a Group I metal or an ammonium cation
(NHx(R.sub.2(y).sup.+, wherein R2 is a C.sub.1 to C.sub.4 alkyl; x
is 1 to 4; y is 0 to 3; and x+y is 4.
[0051] In a preferred embodiment, the fluorosurfactant may consist
of the anionic fluorosurfactant of formula III:
(R.sub.fCH.sub.2CH.sub.2O)P(O)(ONH.sub.4).sub.2 Formula III
[0052] wherein R.sub.f is a C.sub.4 to C.sub.8 perfluoroalkyl group
having the formula: F[CF.sub.2--CF.sub.2].sub.3-8. In preferred
embodiments, the fluorosurfactant is a solvent-free anionic
fluorosurfactant. Suitable anionic fluorosurfactants are
commercially available.
[0053] In some embodiments, surfactant composition according to the
present invention is at least substantially free or free of
cationic fluorosurfactants. According to some embodiments, the
fluorosurfactant may be present in an amount ranging from about
0.05 wt. % to about 4 wt. % based on the total weight of the powder
coating. In a preferred embodiment, the fluorosurfactant may be
present in an amount ranging from about 0.7 wt. % to 3 wt. % based
on the total weight of the powder coating. In some embodiments, the
fluorosurfactant may be present in an amount ranging from about 1.5
wt. % to 3 wt. %, alternatively from about 0.1 wt. % to 0.3 wt. %
based on the total weight of the powder coating. According to some
embodiments, the fluorosurfactant may be present in an amount
ranging from 10 wt. % to 25 wt. % based on the total weight of a
pigment--including all sub-ranges and integers there between.
[0054] According to some embodiments of the present invention, the
pigment, e.g., titanium dioxide, may be pretreated with the
surfactant composition prior to be added to the precursor mixture.
In a preferred embodiment, the pigment is pretreated with anionic
fluorosurfactant according to the following steps: heating the
anionic fluorosurfactant composition of the present invention to an
elevated temperature to melt the anionic fluorosurfactant, which
may range from 50.degree. C. to 70.degree. C. (including all
integers and sub-ranges therebetween), followed by the addition of
the titanium oxide. The anionic fluorosurfactant and the pigment
are then mixed, thereby creating the pretreated titanium dioxide
pigment. In some embodiments, the elevated temperature may be
55.degree. C. The pretreated pigment can be cooled to room
temperature and later mixed with the binder and cross-linker to
form the precursor mixture, as discussed herein. In a preferred
embodiment, the pigment is titanium dioxide that is pretreated with
the anionic fluorosurfactant of formula III. It has been found that
pretreating the pigment with the fluorosurfactant before the other
ingredients of the coating compositions are added to produce the
coating composition mixture ensures uniform dispersion of the
fluorosurfactant in the coating composition.
[0055] According to some embodiments of the present invention, the
binder, cross-linker, and additives and fillers may be combined
into a single precursor mixture. The precursor mixture may be
lightly mixed at room temperature by a dry blender for a period of
time, thereby creating an evenly distribution of binder,
cross-linker, and additives/fillers in the precursor mixture. After
dry blending, the precursor mixture may be melt-mixed and
pelletized according to the discussion herein.
[0056] According to some embodiments of the present invention, the
precursor mixture may be processed in a melt extruder. The melt
extruder may be a single screw or twin screw extruder. The melt
extruder may comprise three zones: (1) a feed zone; (2) a melt
zone; and (3) dispersion zone. The feed zone may be held at a
temperature that is less than or equal to room temperature to
prevent blockages of the precursor mixture. The melt zone is
generally heated above the maximum Tg of the precursor mixture but
below the de-blocking and reaction temperature of the precursor
mixture. Operating between above the Tg and below the
de-blocking/reaction temperature allows the precursor mixture to
become molten and flow without the precursor mixture prematurely
deblocking and reacting inside of the extruder. In the dispersion
zone, the temperature is maintained above the Tg and below the
deblocking temperature, thereby allowing the precursor mixture to
become a uniform. In some embodiments, the melt zone and dispersion
zone are operated at a temperature ranging from about 90.degree. C.
to 150.degree. C.--including all subranges and integers
therebetween. In some embodiments, the melt zone and dispersion
zone are operated at a temperature ranging from 100.degree. C. to
110.degree. C. The extruder will comprise a heating means and a
cooling means to ensure that the various zones stay within the
appropriate temperature ranges.
[0057] After passing through the dispersion zone, the melt-mixed
precursor mixture passed through an extruder exit die. The exit die
may be provided with a plurality of apertures in a number of
different configurations. In some embodiments, the exit die may be
replaced by other devices which allow for a pressure drop across
them; for example, such a pressure drop could be achieved using a
particular screw configuration. In any event, the average residence
time of the precursor mixture in the melt extruder will generally
be less than 5 minutes and more typically in the range from 30 to
120 seconds. As the molten precursor mixture passes through the
die, it is cooled, and pelletized. The pellets are ground and the
resulting precursor powder is then collected. In some non-limiting
embodiments, the precursor mixture may be ground by machine, such
as a grinder, cryogenically grinder, or the like. The resulting
precursor powder may have an average particle size of less than 100
.mu.m, typically ranging from 30 to 50 .mu.m.
[0058] According to some embodiments, a predetermined amount of the
precursor powder may then be placed in a container, which is either
placed into storage or shipped to another location for final
processing, as discussed herein. In other embodiments, the
precursor powder may finally processed at the same site as the
melt-mixing. According to the present invention, final processing
includes spray coating or electrostatic coating the precursor
powder onto a substrate. The spray coating may applied by a spray
gun in an electrostatic field or with a triboelectric gun in which
the powder is charged by friction. The substrate according to the
present invention may be a metallic substrate, ceramic substrate,
composite substrate, or a combination thereof. In some embodiments,
the metallic substrate may be an aluminum panel or a steel panel
(including galvanized steel). According to some embodiments, the
metallic substrate may be selected from materials such as iron,
steel, aluminum, tin, and alloys thereof. The substrate may
comprise any suitable dimensions suitable for ceiling panel
applications.
[0059] After the precursor powder is spray coated onto the
substrate, the resulting spray coating is cured by heating in an
oven at a curing temperature that is above the deblocking and
reaction temperature of the precursor mixture. In some embodiments,
the curing temperature ranges from about 160.degree. C. to
210.degree. C. Curing may occur for a period of time sufficient for
the binder and cross-linker to fully react, thereby forming the
fully cured powder coating. In some embodiments, the curing occurs
for a period of time ranging from 15 to 30 minutes for temperature
ranging from about 160.degree. C. to 190.degree. C. In some
embodiments, the curing may occur for a period of time ranging from
about 6 to 15 minutes for temperatures ranging from about
190.degree. C. to 210.degree. C. The resulting cured powder coating
and substrate form the dirt and/or soil repellent panel of the
present invention. In some embodiments, the resulting powder
coating has a thickness ranging from 40 um to 120 um including all
sub-ranges and integers included there between.
[0060] According to some embodiments the powder coating of the
present invention may be radiation curable by comprising the
aforementioned acrylate-functional polymers. The present invention
is illustrated with thermoset powder coating compositions. However,
thermoplastic powder coating compositions can also be used.
[0061] The following examples are prepared in accordance with the
present invention. The present invention is not limited to the
examples described herein.
EXAMPLES
[0062] The examples according to the present invention are based on
polyester powder coatings and polyurethane powder coatings. Each
powder coating is the reaction product of a number of binders and
cross-linkers. The specific reactants used in the examples are
listed as follows: [0063] i. Binder 1: Carboxylated polyester resin
having 100% solids content (in granule form at room temperature);
melt viscosity of about 5,000 mPa/s at 200.degree. C. (4,400 to
5,700 mPa/s at 200.degree. C.); Tg of about 70.degree. C.
(67.degree. C.); acid value of about 33--commercially available as
Crylcoat 2441-2; [0064] ii. Binder 2: glycidyl-functional acrylic
copolymer having 100% solids content (flaked powder at room
temperature); softening point of 120.degree. C. to 135.degree.
C.--commercially available as Isocryl EP-540; [0065] iii. Binder 3:
hydroxyl-terminated polyester resin having 100% solids content;
melt viscosity ranging from 2,100 to 3,000 mPa/s at 200.degree. C.;
Tg of about 50.degree. C. (48.degree. C.-53.degree. C.); OH value
of about 290; acid value of about 11--commercially available as
Polymac 3110; [0066] iv. Binder 4: hydroxyl-terminated polyester
resin having 100% solids content, melt viscosity of 4,000 mPa/s at
200.degree. C.; Tg of about 60.degree. C. (59.degree. C.); OH value
of 40; acid value of 13--commercially available as Rucote 102;
[0067] v. Cross-linker 1: .beta.-hydroxyalkylamides (HAA) having a
solids content of 100 wt. %; melting point of 120.degree. C. to
124.degree. C.; OH value of 620 to 700--commercially available as
Primid XL-552; and [0068] vi. Cross-linker 2: .epsilon.-caprolactam
blocked IPDI having 100% solids content; Tg of about 60.degree. C.
(58.degree. C.); NCO eq. weight of 280--commercially available as
Alcure 4402.
[0069] According to the present invention, the polyester (PE) and
polyurethane (PU) formulations are shown in Table 1 as follows:
TABLE-US-00001 TABLE 1 PE Formulation 1 PU Formulation 1 Binder 1
80.5 wt. % -- Binder 2 17 wt. % -- Binder 3 -- 28.8 wt. % Binder 4
-- 20.5 wt. % Binder 5 -- -- Cross-linker 1 2.5 wt. % --
Cross-linker 2 -- 50.7 wt. % Total 100 wt. % 100 wt. %
[0070] PE Formulation 2 is a polyester resin mixed with an epoxy
functional cross-linker that contains of conventional titanium
dioxide particles--commercially as Interpon D1036 from
AkzoNobel.
[0071] PE Formulation 3 is a polyester resin mixed with an epoxy
functional cross-linker that contains of conventional titanium
dioxide particles--commercially available from AkzoNobel as
Interpon EC544.
[0072] The examples of the present invention compare pigments that
have been pre-treated with surfactant as well as not pretreated
with surfactant--wherein the pretreated pigments include surfactant
an anionic fluorosurfactant as well as relevant comparisons to
other surfactants. The specific pretreated pigments are as follows:
[0073] i. Surfactant Composition 1 has 100% solids and comprises
the anionic fluorosurfactant ammonium C6-C16 perfluoroalkylethyl
phosphate, which is available from Sensient under the tradename
Unipure.TM. LC981, as a cosmetic ingredient. [0074] ii. Surfactant
Composition 2 has 100% solids and includes an anionic
fluorosurfactant having a phosphate group The anionic
fluorosurfactant has a melting temperature between 50.degree. C.
and 70.degree. C. and a pH value between 1 and 5. An exemplary
suitable anionic fluorosurfactant is commercially available from Du
Pont, under the tradename Capstone.RTM. FS-66. [0075] iii.
Surfactant Composition 3 comprises a non-ionic fluorosurfactant.
The surfactant composition 2 having a 100% solids content and a pH
ranging from 7-8.5. An exemplary non-ionic surfactant is
commercially available Capstone.RTM. FS-3100. [0076] iv. Surfactant
Composition 4 has 100% solids and comprises a monomeric
fluorosurfactant having the formula of:
C.sub.4F.sub.9--CH.dbd.CH.sub.2. The monomeric fluorosurfactant has
a boiling point of 58.degree. C. and a viscosity of 7 mPa/s at
25.degree. C. An exmplary monomeric fluorosurfactant is
commercially available Capstone.RTM. 42-U. [0077] v. Surfactant
Composition 5 has 100% solids content and comprises a nonionic
siloxane-based surfactant. The siloxane containing surfactant is
commercially available Dynol.RTM. 960 from Air Products.
[0078] The surfactants, other than the fluorosurfactant of
Surfactant Composition 1, are then used to pretreat titanium oxide
powder according to the following methodology. Each of the
surfactant composition is separately heated to 55.degree. C. and
subsequently mixed with an amount of titanium dioxide particles for
a period of time. After the period of time, the pretreated titanium
dioxide particles are cooled to room temperature and mixed with the
various PU or PE formulation, as shown below in Table 2, thereby
creating the precursor mixtures. The mixing of PU or PE formulation
with the pretreated titanium is additional step is not required,
however; it enhances the uniformity of the resultant system.
[0079] Each precursor mixture is then melt-mixed by extruder at a
temperature ranging between 95.degree. C. and 108.degree. C. Each
resulting extrudate is pelletized into powder. Each resulting
powder is spray coated onto a first major surface of an aluminum
substrate. The coated substrate is then heat cured at a temperature
of 195.degree. C., thereby producing the dirt repellant panel.
[0080] Each dirt repellant panel is then compared for dirt
repellency according to the follow methodology. A dirt composition
is prepared having components displayed in Table 2:
TABLE-US-00002 TABLE 2 Component Wt. % Peat Moss 35 Portland Cement
15 Calcined Kaolin 15 Sno-Brite Clay 15 NaCl 5 Gelatin 3.6 Carbon
Black 1.5 Red Iron Oxide 0.3 Stearic Acid 2.2 Oleic Acid 2.2 Palm
Oil 3.8 Lanolin 1.4
[0081] Sno-Brite Clay includes >95 wt. % Kaolin as well as minor
amounts of silica (quartz, cristobalite), mica, and titanium
dioxide. Each dirt repellent panel is positioned such that the
powder coated surface faces upward. An amount (0.2 grams) of the
dirt composition of Table 2 is then placed into a plastic cup and
held over the powder coated surface, where the plastic cup is
tapped allowing the dirt composition to fall naturally onto the
upward facing powder coated surface of the dirt repellant panel.
Except for the dirt composition that is applied to the powder
coated surface, the dirt repellant panel remains untouched. The
soiled dirt repellant panel is then left for a period of 24
hours.
[0082] After the period of 24 hours, the dirt repellent panel is
flipped upside down (180.degree.) causing the powder coated surface
to face downward, allowing the loose dirt composition to fall off
of the powder coated surface of the dirt repellant panel. The
surface of the dirt repellant pane that is opposite the powder
coated surface is then tapped 20 times causing additional dirt
composition to fall off of the dirt repellant panel. The dirt
repellant panel is then turned half way back (90.degree.) such that
the powder coated surface of the dirt repellant panel is facing
sideways, followed by tapping the side of the dirt repellent panel
10 times. The dirt repellent panel is then turned back to the
original position such that the powder coated surface is facing
upwards, where the powder coated surface is then measured for a
change in color value--i.e. "Delta E" (.DELTA.E).
[0083] Delta E value is measured by the following calculation:
.DELTA.E=[(L.sub.2-L.sub.1).sup.2+(a.sub.2-a.sub.1).sup.2+(b.sub.2-b.sub-
.1).sup.2].sup.1/2
[0084] wherein L.sub.1, a.sub.1, and b.sub.1 are each initial color
values of an unsoiled dirt repellant panel that are measured using
a Minolta Chroma Meter CR 410 from Minolta Corporation. The
L.sub.2, a.sub.2, and b.sub.2 values are the color values as
measured by the Minolta Chroma Meter CR 410 after each sample is
soiled by the dirt composition, as previously discussed. The
various color readings are taken at three different areas on the
sample, and the average Delta E is recorded--as shown in Table 3.
The control sample for each test item is of the same color and
construction as the test item.
TABLE-US-00003 TABLE 3 Ex. 1 Ex. 2 Ex.3 Ex. 4 Ex.5 Ex. 6 Ex. 7 Ex.
8 Ex. 9 PE Formulation 1 64.6 -- 64.6 65 -- -- -- -- -- PE
Formulation 2 -- -- -- -- -- -- -- -- 65 PE Formulation 3 -- -- --
-- -- -- -- -- -- PU Formulation 1 -- 33.7 -- -- 33.7 33.7 33.9
32.8 -- Surfactant Comp. 1 -- -- 1 0.5 1 0.75 0.5 3 -- Surfactant
Comp. 2 1 1 -- -- -- -- -- -- -- Surfactant Comp. 3 -- -- -- -- --
-- -- -- 0.5 Titanium Dioxide (g) 20 20 20 20 20 20 20 20 20
Additional Component* 14.4 8.1 14.4 14.5 45.3 45.55 45.6 44.2 14.5
Total 100 100 100 100 100 100 100 100 100 .DELTA.E 1.70 2.4 5.04
15.92 0.81 0.33 1.68 1.11 22.73 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14
Ex. 15 Ex. 16 Ex. 17 PE Formulation 1 64.6 65 -- 64.6 65 -- -- --
PE Formulation 2 -- -- -- -- -- -- 100 -- PE Formulation 3 -- -- --
-- -- -- -- 100 PU Formulation 1 -- -- 37.7 -- -- 33.7 -- --
Surfactant Comp. 1 -- -- -- -- -- -- -- -- Surfactant Comp. 3 -- --
-- -- -- -- -- Surfactant Comp. 4 1 0.5 1 -- -- -- -- -- Surfactant
Comp. 5 -- -- -- 1 0.5 1 -- -- Titanium Dioxide (g) 20 20 20 20 20
20 -- -- Additional Component* 14.4 14.5 45.3 14.5 8.1 45.3 -- --
Total 100 100 100 100 100 100 100 100 .DELTA.E 28.15 22.74 34.98
21.47 29.33 37.74 27.68 24.00 *Additional component: flow and
leveling agents, non-pretreated pigments, and fungicides. For the
polyurethane formulations, additional components include an
effective amount of dibutyl tin dilaurate (about 0.5 wt. % based on
entire weight of powder coating).
[0085] As shown in Table 3, the powder coatings based on the
anionic fluorosurfactants (Examples 1-8) performed greater than the
non-ionic surfactant (Example 9), monomeric surfactants (Examples
10-12), and siloxane containing surfactants (Examples 13-15).
Examples 16 and 17 are control examples that are powder coatings
containing titanium dioxide that has not been pretreated with a
surfactant. Furthermore, as demonstrated by Examples 5-8 there is a
marked improvement in performance properties when using
polyurethane based powder coating as compared to the polyester
based powder coating of Examples 3 and 4. Further, Examples 5 and 6
show a higher Delta E with less anionic fluorosurfactant in a
polyurethane system compared to the Delta E of Example 8.
[0086] As those skilled in the art will appreciate, numerous
changes and modifications may be made to the embodiments described
herein, without departing from the spirit of the invention. It is
intended that all such variations fall within the scope of the
invention.
* * * * *